Make sure that you get a power supply that is big enough - the new AMDs would do best with at least a 350, I am running an Athlon XP 2000+ with a moderate number of components and a 400 watt. I do like Antecs though because they have a smart fan that runs at the speed that the system need to keep cool.
Sorry should ahve read your post better - but you will need at least a 400 watt in my opinon, but it can't hurt to get too big of a power supply, it will last for several upgrades.